Heat butter or olive oil in a small non-stick skillet over medium low heat.

Whisk together egg whites, salt, pepper and pesto, whisking in a lot of air.

Pour whisked egg mixture into the heated skillet. Shake skillet back and forth over heat for less than one minute. Run a spatula around the outside of the skillet, tilting skillet to allow excess egg whites to flow into the open space. Sprinkle the cheese over one half of the egg whites. With spatula, flip the other half over cheese Cook until cheese is melted.

Pour spaghetti sauce into a small glass container, microwave for a few seconds to warm sauce.

Slide omelette onto a serving plate. Spoon a small amount of warm sauce over omelette.